1. Field of the Invention
The invention relates to a mechanism for exchanging chip-carrier plates in a hybrid chip-bonding machine, in particular to an automatic hybrid chip-bonding machine.
2. Description of the Related Art
A hybrid chip-bonding machine is used to bond semiconductor chips of various types, and in particular of different sizes, to a substrate. In the delivery stage chips are transported individually to a system that detaches the chips and sends them to a suitable receiving tool. A variety of chip-delivery systems are known and in use, and the choice of such a system is determined primarily by the size of the chip. The available chip-delivery systems include, for example, wafer rings or carrier-film frames and waffle packs, also called gel packs, each of which can be obtained in various sizes.
For automatic hybrid chip bonding the machine must be capable of handling a number of different sizes or types of chips while requiring the shortest possible time for changing from one size or type of chip to another, so that the machine running time is interrupted only briefly.
Each individual wafer, each carrier-film frame or each waffle pack or gel pack in any of the known chip-transporting systems contains chips of only a single type or size. If during the bonding process it becomes necessary to change from one type or size of chip to another, it is also necessary to change to another chip-carrier plate, even though the carrier plate may be of the same type, and the only difference resides in the chips that are being delivered. In known hybrid chip-bonding machines the chip-carrier plates are exchanged individually, which lengthens the production time.
The applicant's patent EP 0 447 082 B 1 discloses a mechanism for exchanging chip-carrier plates that is designed for use in a hybrid chip-bonding machine, in particular an automatic hybrid chip-bonding machine. In this case an automatic hybrid chip-bonder comprises a chip-carrier-plate system, a station for detaching the chips, and a system for receiving and mounting the chips, which may consist of a die collet system or an epoxy die bonder.
The chip-detaching system according to the applicant's patent EP-A-0 447 083 comprises a carrier, a plurality of chip-detaching heads mounted on the carrier, and a device for the stepwise advancement of the carrier so as to move a head incrementally into an operating position. The various heads bear chip-detaching pins in different arrangements, each one suitable for detaching a particular size or type of chip. After it has been detached, the chip is taken up by a suitable receiving means and transported to a chip assembly station.
The chip-receiving stage advantageously comprises a system for exchanging tools such as is described in the applicant's patent EP-A-0 447 087. This includes a set of tools with a plurality of tool holders, into each of which a tool is inserted and which are configured so as to be received by a head. The head is mounted on a holder and can be driven between the set of tools, the chip-detaching system and a chip-assembly station. The set of tools can be driven in such a way as to pass a selected tool holder on to a station at which it can be taken up by the head.
The system for exchanging chip-carrier plates according to the above-mentioned EP 0 447 082 B1 comprises:    (a) a magazine to store a plurality of chip-carrier plates,    (b) a transport arrangement attached to an axial peg that can be rotated about its vertical axis and incorporates a first and a second clamping device, which are attached to a rotatable holder, such that each clamping device is designed to collect a selected chip-carrier plate from the magazine, guide it to a chip-detaching system of the chip-bonding machine, remove it from the chip-detaching system after a predetermined number of chips have been detached, and return it to the magazine,    (c) a switching means to shift the carrier plates within the magazine, so that the selected carrier plate is positioned at a collection point for collection from the magazine, and    (d) a switching means to rotate the transport arrangement further about the above-mentioned vertical axis.